Quick-acting reversing valve with pressure compensation



April 3, 1962 H. K. J. VAN DEN BUSSCHE 3,027,880

QUICK-ACTING REVERSING VALVE WITH PRESSURE COMPENSATION Filed June 14,1960 2 Sheets-Sheet 1 FIG.3

INVENTOR H.K.J. VAN DEN BUSSCHE BY mam.-

IS AGENT April 3, 1962 H. K. J. VAN DEN BUSSCHE 3,027,880

QUICK-ACTING REVERSING VALVE WITH PRESSURE COMPENSATION Filed June 14,1960 2 Sheets-Sheet 2 FlG.4

H. K.J. VAN DEN BUSSCHE';

BY IS AGENT United States The invention relates to a quick-acting valvefor automatically reversing the supply and the discharge of pressuremedium respectively to or from the working space of a double-actingcylinder containing a working piston, which valve comprises a stationaryhousing provided with ports, a free valve body contained in the housingand cooperating with the said ports, and two cylinder spaces extendingalong the longitudinal axis of the valve body, which spaces are eachbounded at one side by the said valve body, and a control member adaptedto be adjusted with respect to the valve body by the working piston foralternately connecting the cylinder spaces to the pressure medium inletand the pressure medium outlet.

Quick-acting valves of the above type are especially suitable foroperating hydraulic piston engines, since the use of such valvescompletely eliminates a stoppage period of the working piston at the endof the stroke thereof, which occurs when conventional valves areemployed. The quick-acting valve of the present invention may be used inoperating a hydraulic piston engine as described in co-pending US.patent application Serial No. 842,363,

filed September 25, 1959, now Patent No. 2,965,077

issued on December 20, 1960.

It has been found, however, that the stroke of the working piston of ahydraulic piston engine provided with a quick-acting valve of theabove-mentioned type is not constant under all conditions, but increaseswith decreasing load of the piston engine. As a result the piston wouldabut against the cylinder covers when it is in its end position so thatthere is another stoppage period at the end of the stroke. The higherthe load, the shorter will be the piston stroke, which means that inorder to ensure that the total travel of the piston per unit of time isconstant (which is desired, for example, when the engine drives a pistonpump giving a required constant output), the frequency has to beincreased which adversely affects the wear (e.g.-, of the valves of apump which is being driven).

The object of the invention is to obviate this drawback.

To this end, according to the invention, the port alternately connectingthe cylinder spaces to the pressure medium inlet is provided with amember which, when the pressure difference between the inlet and theoutlet increases or decreases, reduces or enlarges respectively thepassageway of the port.

This member preferably consists of a pressure-sensitive elementconnected at one side to the medium inlet, and at the other side to themedium outlet, and of a throttle element connected to thepressure-sensitive element and provided in the passageway of the saidport.

The pressure-sensitive element may be a piston-shaped body provided in abore in one of the collars of the valve body.

The invention will be explained with reference to the drawing, wherein:

FIGURES 1, 2 and 3 are diagrams of longitudinal sectional views of thequick-acting valve in three different positions of the valve body andthe control member;

FIGURE 4 is a view in enlarged detail of the part of the valve housingcontaining the control member; and,

FIGURE 5 is a view taken on the line V-V in FIGURE 4.

' atent o" 3,027,888 Patented Apr. 3, 1862 FIGURE 1 shows adouble-acting cylinder 1 containing working piston 2 which is connectedby means of a piston rod to a work-absorbing appliance (not shown). Thepiston rod 3 is coupled to an abutment member 4 and is adapted toadjust, via the latter, the control member 7 of the quick-acting valve 8by way of the two levers 5 and 6. The levers 5 and 6 are pivotallysupported by the fixed fulcrums 9 and 10 and interconnected by a hingedcoupling rod .11. The displacement of the valve may also behydraulically derived from that of the piston as described in the U.S.patent application, Serial No. 842,363, filed September 25, 1959, nowPatent No. 2,965,077 issued on December 20, 1960.

The working spaces 12 and 13 of the cylinder 1 communicate with thehousing 16 of the quick-acting valve 8 through conduits 14 and 15,respectively. The housing 16 is provided with ports 17, 18, 19, 20 and21 of which the port 19 is connected to a hydraulic medium inlet, theports 17 and 21 to a hydraulic medium outlet. Port 18 communicates withworking space 12 through conduit 14 and port 20 communicates withworking space 13 of cylinder 1 through conduit 15.

A free cylindrical valve body 22 is contained in the housing 16 and isprovided with shoulders of enlarged diameter or collars 23 and 24. Anannular space within the valve body 22 is divided into two cylinderspaces 27 and 28 by a piston 26 mounted on a control rod 25 of thecontrol member 7. Abutment members 29 are provided at both ends of thespace enclosed by the housing 16 limiting the extreme positions .of thevalve body 22.

The hydraulic medium is supplied to and discharged from the cylinderspaces 27 and 28 through the inlet opening 30 provided in the valve body22 and through longitudinal grooves 31 and 32 which are provided in thecontrol rod 25.

The member controlling the passageway of the inlet opening 30 independency of the diflference between the inlet pressure and the outletpressure, the parts of which member being shown in FIGURES 4 and 5 on alarger scale than in the FIGURES 1, 2 and 3, comprises a plunger 34adapted to be moved in a bore 33 and coupled to a throttle element 36mounted for movement in a conduit 35 and provided with a profiled fluidport 37. In addition, the plunger 34 is provided with a shoulder 38,between which shoulder and the collar 23 a compression spring 39 isarranged.

The quick-acting valve 8 operates as follows. In FIG- URE 1, the workingpiston 2 is in its extreme right-hand position in the cylinder 1. Inthis case the piston 26 of the control member 7, which control member isconnected to the piston rod 3 of the piston 2 by way of the lever 6, isin such a position relative to the inlet opening 30 of the valve body 22that the cylinder space 28 communicates with the space 40 bounded by thecollars 23 and 24 of the valve body 22 and the housing 16. In thisposition, the said space 40 also communicates with the high-pressureinlet port 19, so that high-pressure hydraulic medium may enter thecylinder space 28. Since, moreover, in this position the cylinder space27 communicates with the outlet port 17 through the groove 31 and thespace to the left of the collar 23, there is a pressure in the space 27which is lower than that in the space 28. Since the pressures prevailingin the spaces to the left of the collar 23 and to the right of thecollar 24 are equal, as both communicate with an outlet port, the valvebody 22, being mounted for free movement in the housing 16, will quicklymove to the right relative to the piston 26. This movement continuesuntil the valve body 22 abuts against the abutments 29 provided on theright-hand side of the housing 16. In this position (see FIGURE 2) thecollar 23 is between the ports 18 and 19 and the collar 24 between theports 20 and 21. Consequently, communication is established between theconduit 14 and the outlet port 17 through the port 18, and between theconduit and the inlet'port 19 through the port 20. As a result, theworking piston 2 will be displaced to the left in the cylinder 1, duringwhich displacement both the valve body 22 and the control member 7remain in the position shown in FIGURE 2 since the pressures on eitherside of the valve body 22 are equal, and the high pressure prevailing inthe space 28 is unable to move valve body 22 relative to control member7, as the piston 26 is already pressed against the left-hand side of thespace Within the valve body 22.

Before the piston 2 reaches its extreme left-hand position (positionshown in dotted lines in FIGURE 1) the control member 7 begins to movetothe right by means of the lever 5, the coupling rod 11 and the lever6, which lever system is started by the abutment means 4 of the pistonrod 3 engaging the lever 6. Inst before the piston 2 reaches the extremeleft-hand position, the piston 26 of the control member 7 exposes theopening (see FIGURE 3) and thus establishes communication between thecylinder space 27 and the high-pressure inlet 19. The communicationbetween the cylinder space 27 and the outlet port 17 through the groove31 is simultaneously broken. In this position the cylinder space 28simultaneously communicates with'the outlet port 21 through the groove32, so that as a result of the pressure difference prevailing betweenthe spaces 27 and 28 the valve body 22 will rapidly move to the leftrelative to the piston 26 mounted on the control device 7. Thisdisplacement is arrested by the abutments 29 mounted on the left-handside of the housing 1 6. The latter position of the valve body 22corresponds with the position shown in FIGURE 1 wherein the supply anddischarge to and from the working spaces 12 and 13 of the cylinder l areinterchanged relative to the position shown in FIGURE 3.

Thus, the movement of the working piston 2 is quickly reversed, andafter the control member 7 has been switched over to the position shownin FIGURE 1 at the end of the subsequent stroke, the cycle describedabove is repeated.

If during operation of the piston engine. the work taken up by thework-absorbing appliance (not drawn) decreases, this decrease in theload on the hydraulic piston engine will be reflected as a reduction inthe supply pressure in the inlet port 19 and the spaces communicatingtherewith. As a result of this reduction in the supply pressure therewill be a decrease in the difference over the pressure-sensitive element34 (see FIGURES 4 and 5) and the throttle element 36 is moved to theright by the action of the compression spring 39. As the profiled port37 of the throttle element 36 in its extreme right-hand position exposesa larger passageway of the opening 30 than in its extreme left-handposition, this displacement will result in a larger passageway of theopening 30., The liquid flowing to the cylinder space 28 through thisopening 3% now meets with less resistance in this opening, so that thepressure drop in the space 28. caused by the pressure drop in the inletport 19 iscompensated. Thus, the force which acts on the valve body 22,and is required for the reversal thereof, is practically unchanged bythe pressure drop in the inlet port 19, and, since the resistance tobeovercome by the, valve body 22 in the reversal is practicallyconstant, the valve body is reversed between its extreme positions inthe same period as was the case before the load o-f the piston engine 1decreased.

v Conversely, theload on thepiston engine 1 increases, the pressure inthe inlet port 19 will also increase. The effect of the resultantincrease of the pressure difference prevailing over the collar 23, isthat the pressure-sensitive element 34 moves to the left against theaction of the compression spring 39. The throttle element 36 then alsomoves to the left and the profiled port 37 of the throttle element 36reduces the passageway of the opening 30. The resistance met by theliquid stream in the opening 30 increases, whereby a pressure dropoccurs in this opening which compensates the pressure rise in the space28 which results from the increase in the load. In this case also thereversing speed of the valve body 22 remain-s unchanged.

The excess travel of the piston 2 in its extreme positions after thepiston 26 has opened the inlet port in the valve body 22, depends on thereversing speed of the valve body 22. Since the invention has providedmeans with which the reversing speed may be kept constant orsubstantially constant at different loads on the piston engine, thelength of the total stroke of the piston 2 in the cylinder 1 alsodepends on the load on the piston engine.

This prevents the piston 2 from abutting against the covers of thecylinder 1 at low loads of the piston engine, which, except for possiblebreakage, has the drawback that there is a period when the piston stopsat the ends of the stroke, whereby the continuity in the delivery ofenergy is broken. The. use of the invention is also importantinhydraulic piston engines adapted to drive an appliance for the properoperation of which a constant stroke is required.

The invention is not limited. to the embodiment of the valve as shown inthe drawing. If desired, the valve body may be designed as a fiat valve.Nor is the invention limited to the embodiment of the pressure-sensitiveelement 34 and the throttle element 36 as shown in the drawing.

It is essential, however, that the. change; in the pressure in the inletopening 19 be compensated by a change in the flow resistance in theopening 30. If in this case the supply pressure is P and the pressuredrop over the opening SOAP, the pressure available for moving the valvebody is P-AP. This difference in pressure PAP should remain constant atvarying supply pressure P. From this it follows that the filling ratethrough the opening 30 (which filling rate equals the product of flowrate V in opening 30 and surface area 0 of the passageway of thisopening 30) is also constant. Since, in addition, the pressure drop APover the opening 30 is proportionate to the square of the rate V inopening 30, the requirement regarding the constant value of thedifference P-AP may also be expressed by the formula P %=eonstant In thelatter formula C is a constant.

If P is increased the movement of the pressure-sensitive element shouldbe such that by narrowing the passage- -way O by the throttle elementthe above requirement is spaces located at both ends of the free valvebody as.

shown in U.S. patent specification 2,361,757.

I claim as my invention:

1. A quick-acting valve for automatically reversing. the 2 supply andthe discharge of pressure medium respectively to and from theworkingspaces of a double-acting cylinder containing a working piston,which valve comprises a stationary housing provided with pressure mediuminlet and outlet ports, a free valve body contained in the housing andfor selectively opening and closing said ports, and a control memberadapted to be adjusted by the working piston and forming within thevalve body two cylinder spaces, the control member being provided with,a piston forming a partition between the cylinder spaces which arealternately connected to the pressure medium inlet and the pressuremedium outlet ports through the displacement of the valve body relativeto the control member, a port in said valve body alternately connectingthe cylinder spaces to the pressure medium inlet, pressure-responsivevariable opening throttle valve means for controlling fluid flow throughsaid port in said valve body in response to changes in the pressuredifference between the inlet and the outlet pressure medium ports.

2. The quick-acting valve of claim 1, wherein the pressure-responsivevalve means comprises a pressure-sensitive element in communication onone side to the medium inlet pressure and on the other side to themedium outlet pressure, and a throttle element connected to thepressuresensitive element and positioned in the said port.

3. A quick-acting valve as claimed in claim 2, wherein thepressure-sensitive element is constituted by a pistonshaped bodyprovided in a bore in one of the collars of the valve body.

4. A quick-acting valve for automatically reversing the supply and thedischarge of a pressure medium respectively to and from the workingspaces of a double-acting cylinder containing a working piston, saidvalve comprising a stationary valve housing provided with a port incommunication with each working space of said double-acting cylinder,inlet port means intermediate the ends of said valve housing adapted tocommunicate with a source of hydraulic pressure fluid, discharge portmeans for discharging a hydraulic pressure fluid from said valvehousing, a free valve body having a chamber formed longitudinallytherethrough and being mounted for sliding movement within said valvehousing, a pair of spaced collars of enlarged diameter carried outwardlyon said valve body and providing flow passages on the outside thereof,the spacing between the collars being such that the hydraulic pressurefluid inlet port means at any time is in communication with only one ofsaid housing ports in communication with a working space of saiddoubleacting cylinder, fluid port means through the wall of said valvebody intermediate the collars, a control member extending through thechamber of said valve body and out at least one end of said valvehousing, said control member adapted to be operatively connected to andpositioned by the working piston of said double-acting cylinder, saidcontrol member forming an annular chamber outside thereof in said valvebody, a piston carried on said control member dividing said annularspace into two annular spaces, said piston being slidably movable withsaid control member and so positioned thereon to place the annularspaces alternately in communication with the port means through the wallof said valve body, throttling flow passage means formed longitudinallyin the surface of said control member on opposite sides of said piston,said throttling flow passage means having an eifective length so as tobe closed when the annular space on one side of the piston is in opencommunication through the port in the wall of valve body, anddiflerential pressure responsive valve means in communication with saidhydraulic pressure fluid for controlling the flow of fluid through theport in the wall of said valve body.

5. A quick-acting valve for automatically reversing the supply and thedischarge of pressure medium respectively to and from the working spacesof a double-acting cylinder containing a working piston, which valvecomprises a stationary housing provided with pressure medium inlet andoutlet ports, a free valve body contained in the housing and forselectively opening and closing said ports, and two cylinder spacesextending along the longitudinal axis of the valve body, which spacesare each bounded at one side by the said valve body, and a controlmember adapted to be adjusted with respect to the valve body by theworking piston for alternately connecting the cylinder spaces to thepressure medium inlet and the pressure medium outlet ports, a port insaid valve body alternately connecting the cylinder spaces to thepressure medium inlet, and pressure-responsive variable opening throttlevalve means for controlling fluid flow through said port in said valvebody in response to changes in the pressure difference between the inletand the outlet pressure medium ports.

References Cited in the file of this patent UNITED STATES PATENTS2,361,757 Fink Oct. 31, 1944 2,500,627 Chinn Mar. 14, 1950 2,748,752Baghuis June 5, 1956

